The Concept of a Stare-Mode Astrometric Space Mission

In this paper, we introduce the concept of a stare-mode astrometric space mission. The traditionally accepted mode of operation for a mapping astrometric space mission is that of a continuously scanning satellite, such as the successful Hipparcos and planned Gaia missions. With the advent of astrometry missions mapping out stars to 20th magnitude, the stare mode has become competitive. A stare mode of operation has several advantages over a scanning mission if absolute parallax and throughput issues can be successfully addressed. Requirements for a stare-mode operation are outlined here. The mission precision for a stare-mode astrometric mission is derived as a function of instrumental parameters, and examples are given. The stare-mode concept has been accepted as a baseline for the NASA road map study of the Origins Billions Star Survey (OBSS) mission and the proposed Milliarcsecond Pathfinder Survey (MAPS) microsatellite project.